PubMed · 8249833
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F P Paloucek. 1993. Lead poisoning.. https://doi.org/10.1016/s0160-3450(15)30615-2
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We have developed a method for the detection of biologically relevant derivatives of NO. that couples photolysis to chemiluminescence. S-Nitrosothiols, N-nitroso-L-tryptophan, and iron-nitrosyl derivatives can all be detected by this methodology, and these derivatives can be distinguished from free NO. by making measurements with and without photolysis. The limits of detection of this system are in the 10 nM range, with an intraassay variability of less than 2% and an interassay variability of less than 1.5%. The use of cutoff filters and alterations in pH and flow rate through the photolysis cell provide additional useful parameters with which to characterize specific NO. derivatives based on their intrinsic stability. This methodology is a useful addition to the growing armamentarium of techniques used to characterize the biochemistry and metabolism of NO..
An automated extraction procedure using solid-phase extraction (SPE) disk technology was developed for the qualitative and quantitative determination of ethylenediaminetetraacetic acid (EDTA) in water samples. The procedure involves conversion of all free and chelated EDTA present into the nickel EDTA chelate followed by extraction on strong anion exchange extraction disks, A 5 mL water sample is extracted and concentrated to 30 microL. This extract is then analyzed by capillary electrophoresis (CE) using ion spray-tandem mass spectrometry (MS) for selective detection. An amine-coated capillary column is used to separate anions using negative voltage and high electroosmotic flow. A self-aligning liquid junction is used as the CE/MS interface. The sample is injected using field amplification for enhanced concentration detection limits down to 0.15 microgram/L. This detection limit is about five times lower than any report we have found in the literature and provides the unique specificity afforded by mass spectrometry. Total sample preparation and run time was forty minutes per sample, including evaporation steps and capillary rinsing between runs. A tray of 24 vials, including samples and standards, was analyzed for these experiments and was easily finished within one day. These experiments demonstrate that CE/MS can be a rugged, quantitative technique, which, with proper sample preparation and focusing techniques, can compete with the concentration sensitivity of established analytical methods.
Diffusion of iron is one of the major problems limiting the usefulness of NMR gel dosimetry. This was studied in dual gel samples using a 4.7T micro-imaging MR scanner and a fast T1 imaging sequence which allowed the acquisition of a 64 x 128 x 8 data sets (phase encoding x frequency encoding x number of inversion times) in less than 15 min. The procedure enabled us to obtain relative relaxation times for any region of interest within the sample. After the two differently doped gels were brought into contact in the dual gel samples (diameter 12 mm), the diffusion could be observed on subsequent images as a function of time. An inverse square root function was used to fit the change of 1/T1 across the junction between the two gel phases. A diffusion constant of 0.014 +/- 0.003 cm2/h was determined for Fe3+ in a typical dosimetry gel (1.5% agarose, 50 mM H2SO4). This could be lowered by adding a chelating agent such as xylenol orange to the gel. It was also found that diffusion was slower in gelatine gels, however these gels tended not to set properly when H2SO4 was added as required for NMR dosimetry. From the present results we propose that a gel consisting of 1.5% agarose (for stability), 3% gelatine and 0.1 mM xylenol orange (to combat diffusion and allow a visual evaluation) is a suitable base for NMR dosimetry gels. The use of a fast T1 imaging sequence reduces acquisition times and therefore the potential impact of diffusion.